Only GPS or GPS+IMU as source for Position Plot in Log


Can anybody tell me if the position logged in the telemetry logs are is only from the GPS, or is it an estimate of the position based on the GPS and the IMU?

We are getting wrong position during flight, and then GPS glitch, but unsure if the error is because of the GPS, or if it could also be with the IMU. We do get this problem even if we put some distance between the GPS antenna and the rest of the electronics.